/Engine/Source/Runtime/Core/Public/Math/UnrealMathFPU.h
Double[4] vector register type, where the first double (X) is stored in the lowest 64 bits, and so on.
struct VectorRegister4Double
union VectorReg...
@634
VectorRegister4...
@638
double[4]
V
VectorRegister2...
XY
VectorRegister2...
ZW